Field of the Invention
The present invention relates to a control method for making variations in an ejection amount of individual nozzles unnoticeable in a liquid ejecting apparatus that ejects liquids from a plurality of nozzles respectively.
Description of the Related Art
As inkjet printing apparatuses, in an apparatus that ejects liquids respectively from a plurality of nozzles arranged in a liquid ejection head, there are some cases where variations occur in the amount of liquids ejected from the individual nozzles. In such a case, for example, there occurs a possibility that density unevenness due to the variation in the ejection amount is noticed on a printed image in the inkjet printing apparatus. Therefore, there are conceived various methods for making such a variation in the ejection amount unnoticeable on the image.
For example, Japanese Patent Laid-Open No. 2010-274177 discloses a method in which in a case of manufacturing a color filter using an inkjet technique, one pixel is formed by a predetermined number of nozzles and an average value of the ejection amounts by the predetermined number of the nozzles is uniformed per pixel. According to this configuration, even when there occurs the variation in the ejection amount between the individual nozzles, provided that the ejection amount is adjusted for each group formed of the predetermined number of the nozzles, it is possible to appropriately reduce the density unevenness between the pixels.
In addition, Japanese Patent Laid-Open No. 2004-230672 disclose a method in which, for quantizing multi-valued image data using an error diffusion method, an error generated in the quantization process is corrected according to ejection characteristics of a nozzle corresponding to an individual pixel. When the method disclosed in Japanese Patent Laid-Open No. 2004-230672 is adopted, even if the ejection amount variation of the individual nozzle is not improved, the density is uniformed in some extent of a region on the sheet and the density unevenness can be made difficult to be perceived in visual observation.
However, the method disclosed in Japanese Patent Laid-Open No. 2010-274177 is suitable for the manufacture of the color filter in which the predetermined number of the nozzles can be associated with each of the pixels or the like, and on the other hand, cannot be applied to a case where pixels and dots are associated with each other on a one-to-one basis as in the case of a photo image.
In the method disclosed in Japanese Patent Laid-Open No. 2004-230672, a given density can be obtained in a region having some extent of width, but in a case where an original drawing is not a halftone image like a photo image, but a line drawing configured of fine lines, patterns or the like, the Quantization process is regularly not executed. Therefore there are some cases where the variation in the ejection amount is not corrected and the density unevenness is noticeable. In daring to execute the quantization process as similar to the halftone image, there are some cases where a defect of a dot in the line drawing occurs. In addition, since the density correction is made in the image processing prior to a print operation, it is impossible to preliminarily complete the image processing in a state where a printing apparatus is not associated. As a result, in a case of printing the same image by a plurality of printing apparatuses, the process differs in each of the apparatuses, leading to degradation in working efficiency. Further, in a case of printing by a plurality of printing apparatuses, the density unevenness is improved in the individual image, but the output result possibly differs between the images that are output from the plurality of printing apparatuses. Particularly in a secondary color expressed by a plurality of ink colors in an overlapping manner, the hue possibly differs in each printing apparatus.